The present invention generally relates to stable and water-soluble plant growth regulator compositions with low amounts of volatile organic compounds (VOCs).
Plant growth regulators are useful for influencing a range of plant developmental processes including stem elongation, germination, dormancy, flowering, sex expression, enzyme induction, fruit size and quality, as well as leaf and fruit senescence. Plant growth regulators may be formulated in at least five different types of formulations: 1) solutions, 2) wettable powders, 3) soluble powders, 4) tablets and 5) water-soluble or dispersible granules.
Cytokinins are a class of plant growth regulators which are generally defined as N6-substituted adenine derivatives such as trans-zeatin, 6-benzyladenine (6-BA) and kinetin. Recently, a new class of cytokinins has been identified which possess N-phenylurea substituted structure such as forchlorfenuron (CPPU) and thidiazuron (TDZ). Cytokinins are of extreme importance in regulating plant growth and development, especially cell division. They are marketed under various trade names and are commercially used in fruit thinning and sizing as well as pre- and post-harvest treatments of ornamental plants and flowers.
6-BA and CPPU have very low water solubility of 44 and 39 ppm at 25° C., respectively. Alcoholic solvents such as IPA, THFA and propylene glycol are being employed in conventional liquid plant growth formulations. For example, US Patent Application US 2008/0039322 A1 discloses cytokinin solution formulations comprising propylene glycol. However, one of the disadvantages of alcoholic solvents is that they are considered volatile organic compounds (VOCs) having relatively high photochemical reactivity for ground level ozone formation and, therefore, may be harmful to the environment. The United States Environmental Protection Agency (EPA) estimates the maximum incremental reactivity (MIR) of volatile organic compounds or solvents which can participate in atmospheric photochemical reactions (MIR measures grams ozone produced per grams VOC).
Various regulatory agencies, such as the EPA, the California Department of Pesticide Regulation (DPR) and Air Resources Board (CARB) seek to lower the VOC content in various agricultural products and fumigants.
There is a significant formulation challenge to meet the requirements of lowering the VOC content while preserving product stability and effectiveness.
There is, therefore, a need to develop effective plant growth regulator compositions that contain low amounts of VOCs.